Send mass notifications to users

Currently there is no way to send mass notifications to UMC users from within ARIS.

Add a functionality to the web interface so you can send mails to multiple UMC users at once.

You should be able to enter the subject / content via the web interface and select users or user groups as the recipients. Additionally you should also be able to add normal mail addresses for recipients without ARIS users.

This would be usefull to inform users about maintenance, issues, release updates, ... without having to somehow export their mail addresses and use another software to send the mails (especially with several hundred or thousand users in the UMC).

This should not be tied to any other functionality like collaboration (where users will have to join groups or something like that) or APG.